In Civ4 the graphics and music are seperated this way:

If i rember correctly:
Early (Ancient Era)
Medium (Medieval, Renaissance Era)
Late (if i remmber well Industrial, Modern and Future Era)

Is it any chance to change it or add new types of graphics or sounds (for example separate future era as standalone graphic type - so worker in future will differ from the modern one)?
Where can i find it?

For music the background music is done by era. I think this is possible but I haven't looked into it. All I have seen are the references in the great people entries.

OK thank you

i wan't able to find where can i add new type of graphics in this example Future :(

ok no problem thx for helping :)